Termoelectric heating and cooling apparatus for semiconductor processing

ABSTRACT

A thermoelectric wafer chuck is disclosed. The thermoelectric wafer chuck includes a wafer support surface for supporting a wafer; and a thermoelectric module provided in thermal contact with the wafer support surface for heating and/or cooling the wafer support surface and wafer.

FIELD OF THE INVENTION

The present invention relates to devices for heating wafers in semiconductor processing. More particularly, the present invention relates to a thermoelectric heating and cooling apparatus which is suitable for selectively heating or cooling a wafer during semiconductor processing and is characterized by fast and dynamic temperature control capability and multi-zone implementation.

BACKGROUND OF THE INVENTION

In the fabrication of semiconductor integrated circuits, metal conductor lines are used to interconnect the multiple components in device circuits on a semiconductor wafer. A general process used in the deposition of metal conductor line patterns on semiconductor wafers includes deposition of a conducting layer on the silicon wafer substrate; formation of a photoresist or other mask such as titanium oxide or silicon oxide, in the form of the desired metal conductor line pattern, using standard lithographic techniques; subjecting the wafer substrate to a dry etching process to remove the conducting layer from the areas not covered by the mask, thereby leaving the metal layer in the form of the masked conductor line pattern; and removing the mask layer typically using reactive plasma and chlorine gas, thereby exposing the top surface of the metal conductor lines. Typically, multiple alternating layers of electrically conductive and insulative materials are sequentially deposited on the wafer substrate, and conductive layers at different levels on the wafer may be electrically connected to each other by etching vias, or openings, in the insulative layers and filling the vias using aluminum, tungsten or other metal to establish electrical connection between the conductive layers.

Deposition of conductive layers on the wafer substrate and etching of the layers frequently requires heating and/or chilling of the wafer, depending on the process. Conventional wafer chucks in semiconductor processing chambers which require wafer heating and/or cooling are typically provided with an interior coil through which a heating or cooling liquid or gas is distributed to heat or cool the wafer resting on the chuck through conduction. However, the conventional wafer chucks suffer from various disadvantages, including low wafer-heating response and control, little or no cool-down function, and low wafer temperature control accuracy. Therefore, a new and improved apparatus is needed to facilitate selective heating and/or cooling of wafers during semiconductor processing.

SUMMARY OF THE INVENTION

The present invention is generally directed to a thermoelectric wafer chuck for semiconductor processing. The thermoelectric wafer chuck includes a chuck base and a wafer support surface. Fluid channels extend through the chuck base for distribution of a heating or cooling liquid. A thermoelectric module is provided in thermal contact with the wafer support surface. In use, the thermoelectric wafer chuck is capable of heating a wafer resting on the wafer support surface as the thermoelectric module converts electrical energy into thermal energy according to the Peltier effect. A heating fluid may alternatively or additionally be distributed through the fluid channels in the chuck base to heat the wafer. The wafer is cooled typically by reverse flow of current through the thermoelectric module, by distribution of a cooling fluid through the fluid channels, or both. The thermoelectric wafer chuck facilitates rapid, dynamic and multi-zone temperature control capability of a wafer.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a section of a thermoelectric module suitable for the thermoelectric wafer chuck of the present invention;

FIG. 2 is a front view of the thermoelectric module of FIG. 1;

FIG. 2A is a top view of the thermoelectric module, with a portion of the top isolation plate removed therefrom;

FIG. 3 is a perspective view of a multi-stack thermoelectric module;

FIG. 4 is a perspective view of a section of a thermoelectric wafer chuck of the present invention;

FIG. 5 is a top perspective view, partially in section, of a processing chamber in which the thermoelectric wafer chuck of the present invention is installed, more particularly illustrating flow of a processing gas into the chamber; and

FIG. 6 is a bottom perspective view, partially in section, of the processing chamber of FIG. 5, illustrating multiple heat cells in the thermoelectric module of the thermoelectric chuck.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is generally directed to a thermoelectric wafer chuck for the heating and/or cooling of wafers during semiconductor processing. The thermoelectric wafer chuck includes a chuck base and a wafer support surface. Fluid channels extend through the chuck base in a single-loop or multi-loop configuration for distribution of a cooling or heating liquid through the chuck base. A thermoelectric module is provided in the wafer chuck, in thermal contact with the wafer support surface. The thermoelectric module includes multiple p-type semiconductor connectors and n-type semiconductor connectors adjacent ones of which are alternately connected to each other through top conductor plates and bottom conductor plates. Using the Peltier effect, the thermoelectric module converts electrical energy into thermal energy and is capable of heating a wafer resting on the wafer support surface. Alternatively or additionally, the wafer may be heated by the distribution of a heating fluid through the fluid channels of the chuck base. The wafer may be cooled by reverse flow of electrical current through the thermoelectric module, by distribution of a coolant fluid through the coolant channels in the chuck base, or both. The thermoelectric module imparts rapid, dynamic and multi-zone temperature control capability to the thermoelectric wafer chuck.

The Peltier effect involves the creation of a heat differential from an electric voltage differential. When an electrical current is passed through connectors made of p-type and n-type semiconductors which are connected to each other at two junctions, the current drives a transfer of heat from one junction to the other. Accordingly, one junction of each connector cools while the other heats. P-type silicon typically has a positive Peltier coefficient (though not above ˜550 K), whereas the Peltier coefficient of n-type silicon is typically negative.

As current flows through the connector, the semiconductor material of the connector tends to return to the electron equilibrium which existed prior to application of the current. This is facilitated by the absorption of energy at one junction and the dissipation of energy from the other junction. The coupled pairs of connectors can be connected in series to amplify the thermoelectric effect. The direction of heat transfer is determined by the polarity of the current; therefore, reversing the electrical polarity of the current will reverse the thermal polarity of the junctions.

Referring initially to FIG. 4, a section of an illustrative embodiment of the thermoelectric wafer chuck of the present invention is generally indicated by reference numeral 10. The thermoelectric wafer chuck 10 includes a chuck base 12 which is typically circular. Multiple fluid channels 14 extend through the chuck base 12. Preferably, the fluid channels 14 extend directly through the chuck base 12 without the use of coils, and the thermoelectric wafer chuck 12 is therefore “coil-free”. The fluid channels 14 may extend through the chuck base 12 in a single loop or multi-loop configuration to define one or multiple cooling and/or heating zones 17 a on the chuck 10. A supply (not shown) of a heating or cooling fluid is provided in fluid communication with the fluid channels 14 to distribute a heating or cooling gas or liquid (not shown) through the coolant channels 14 in use of the thermoelectric wafer chuck 10, as will be hereinafter described.

An annular chuck wall 13 extends upwardly from the edge of the chuck base 12. A wafer support plate 16 having a wafer support surface 17 is supported by the chuck wall 13, in spaced-apart relationship to the chuck base 12. A chuck interior 18, the purpose of which will be hereinafter described, is defined between the upper surface of the chuck base 12 and the lower surface of the wafer support plate 16. At least one thermoelectric module 22 is provided in the chuck interior 18. Preferably, a stacked thermoelectric module 22 a, which includes two or more single thermoelectric modules 22, is provided in the chuck interior 18 as will be hereinafter described.

Referring next to FIGS. 1-3, a portion of a single thermoelectric module 22 is shown. Each thermoelectric module 22 typically includes a bottom isolation plate 24 and a top isolation plate 28, each of which is typically ceramic. Multiple bottom conductor plates 26 are provided on the upper surface of the bottom isolation plate 24, and multiple top conductor plates 30 are provided on the lower surface of the top isolation plate 28. The bottom conductor plates 26 and top conductor plates 30 are an electrically-conductive material, typically copper. As further illustrated in FIG. 2, each of the bottom conductor plates 26 overlaps a pair of adjacent top conductor plates 30. On respective sides of the thermoelectric module 22, the bottom conductor plates 26 are shown as terminal plates 26 a and 26 b, respectively, on the upper surface of the bottom isolation plate 24.

Multiple n-type connectors 32 and p-type connectors 34 are connected to each other in series through the bottom conductor plates 26 and top conductor plates 30. Each n-type connector 32 of each series spans a bottom conductor plate 26 and a top conductor plate 30, and the adjacent p-type connector 34 of the series spans the same top conductor plate 30 and the adjacent bottom conductor plate 26. The next n-type connector 32 in the series contacts the same bottom conductor plate 26 as is contacted by the previous p-type connector 34 and a different top conductor plate 30. Accordingly, proceeding from left to right in FIG. 2, each adjacent pair of bottom conductor plates 26 is connected through an n-type connector 32 and a p-type connector 34, respectively, whereas each adjacent pair of top conductor plates 30 is connected through a p-type connector 34 and an n-type connector 32, respectively. In the foregoing manner, all of the n-type connectors 32 and the p-type connectors 34 in the thermoelectric module 22 are interconnected in series through the bottom conductor plates 26 and the top conductor plates 30. A negative electrical lead 36 (which may serve as either a negative or positive electrical lead depending on the desired thermal polarity of the thermoelectric module 22) is electrically connected to the terminal plate 26 a, and a positive electrical lead 38 (which may be positive or negative) is electrically connected to the terminal plate 26 b.

As shown in FIG. 3, in the thermoelectric chuck 10 (FIG. 4), at least two single thermoelectric modules 22 are preferably stacked and electrically connected to each other in series to form a stacked thermoelectric module 22 a. In FIG. 3, the negative lead 36 is connected to the lower thermoelectric module 22, whereas the positive lead 38 is connected to the upper thermoelectric module 22, of the stacked thermoelectric module 22 a. The upper and lower thermoelectric modules 22 are electrically connected in series to each other in the stacked thermoelectric module 22 a through an electrical connector 40.

Referring again to FIG. 4, the stacked thermoelectric module 22 a is provided in the chuck interior 18 of the thermoelectric wafer chuck 10. Alternatively, a single thermoelectric module 22 may be provided in the chuck interior 18. In the former case, the bottom isolation plate 24 (FIG. 3) of the bottom thermoelectric module 22 in the stacked thermoelectric module 22 a rests on the upper surface of the chuck base 12, whereas the top isolation plate 28 of the top thermoelectric module 22 in the stacked thermoelectric module 22 a thermally contacts the lower surface of the wafer support plate 16. In the thermoelectric chuck 10, multiple, independently-controlled single thermoelectric modules 22 or stacked thermoelectric modules 22 a may be provided in the chuck interior 18 in adjacent or concentric relationship to each other or may be otherwise positioned with respect to each other to form multiple, independently-controlled heating zones 17 a on the wafer support surface 17 during operation of the thermoelectric wafer chuck 10. While the heating zones 17 a shown in FIG. 4 are concentric, it is understood that the heating zones 17 a may be arranged in any desired configuration on the wafer support surface 17.

Referring next to FIGS. 5 and 6, the thermoelectric wafer chuck 10 is mounted in a processing chamber 44, which may be a lithography scanner and track, an etching chamber, a CVD (chemical vapor deposition) chamber, a PVD (physical vapor deposition) chamber or other processing chamber in which heating and/or cooling of a wafer are needed. The processing chamber 44 typically includes a chamber wall 46 which defines a chamber interior 48 and includes a gas inlet 50 in the top thereof for the introduction of processing gases 54 into the chamber interior 48. As shown in FIG. 6, multiple gas outlets 52 are provided typically in the bottom of the processing chamber 44. In the bottom view of FIG. 6, in which the thermoelectric wafer chuck 10 is shown in section, the n-type connectors 32 and p-type connectors 34 are shown as heat cells which facilitate heating and/or cooling of a wafer (not shown) resting on the wafer support surface 17 of the thermoelectric wafer chuck 10 during fabrication of semiconductors on the wafer, as will be hereinafter described.

In operation of the thermoelectric wafer chuck 10, a wafer (not shown) is initially placed on the wafer support surface 17 of the chuck 10 in the chamber interior 48 of the processing chamber 44. Depending on the type of processing to be carried out on the wafer, processing gases 54 (FIG. 5) may be introduced into the chamber interior 48 through the gas inlet 50. Simultaneously, the wafer may be heated by operation of the thermoelectric wafer chuck 10. Accordingly, electrical current is distributed through the stacked module 22 a by facilitating flow of current through the negative lead 36, the stacked module 22 a and the positive lead 38, respectively. In the stacked module 22 a, the electrical current flows in series through the bottom conductor plates 26, the n-type connectors 32, the p-type connectors 34 and the top conductor plates 30. As it flows through the n-type connectors 32 and the p-type connectors 34, the electrical current, via the Peltier effect, drives a transfer of heat from the bottom conductor plates 26 to the top conductor plates 30. This results in the production of a cold side at the bottom isolation plate 24 and a heat sink (or hot side) at the top isolation plate 28 of the stacked thermoelectric module 22 a. Consequently, the top isolation plate 28 heats the wafer support plate 16 and wafer support surface 17 of the wafer chuck 10 to a desired set point temperature. At that point, flow of current through the stacked module 22 a may be terminated or intermittently distributed through the stacked module 22 a as needed to maintain the wafer support surface 17 as close as possible to the set point temperature. Alternatively or additionally, a heating fluid (not shown) may be distributed through the fluid channels 14 of the chuck base 12 to heat the wafer by conduction through the stacked thermoelectric module 22 a and wafer support plate 16.

When subsequent cooling of the wafer is necessary, flow of electrical current through the stacked module 22 a is terminated and/or flow of the heating fluid through the fluid channels 14 is stopped. Accordingly, electrical current is distributed in the reverse direction through the positive lead 38, the stacked module 22 a and the negative lead 36, respectively. In the n-type connectors 32 and the p-type connectors 34, this drives a transfer of heat from the top conductor plates 30 to the bottom conductor plates 26, resulting in the production of a cold side at the top isolation plate 28 and a heat sink (or hot side) at the bottom isolation plate 24. Consequently, the top isolation plate 28 absorbs heat from the wafer through the wafer support plate 16 and wafer support surface 17 until the wafer reaches the desired set point temperature. At that point, flow of current through the stacked module 22 a may be terminated or intermittently distributed through the stacked module 22 a as needed to maintain the wafer support surface 17 at the set point temperature. Alternatively or additionally, a coolant fluid (not shown) may be distributed through the coolant channels 14 of the chuck base 12 to absorb heat from the wafer through the wafer support plate 16 and stacked module 22 a, respectively, until the desired set point temperature of the wafer is achieved.

It will be appreciated by those skilled in the art that the thermoelectric wafer chuck 10 of the present invention facilitates rapid, dynamic and uniform wafer heating and cooling capability of wafers, as well as zonal heating and/or cooling of wafers during processing, as needed. Furthermore, the thermoelectric wafer chuck 10 is adaptable for heating and/or cooling wafers in any of a variety of processing chambers or processes including but not limited to lithography, etching, CVD (chemical vapor deposition), PVD (physical vapor deposition) or any other processes in which heating and/or cooling of wafers is needed during fabrication of semiconductors.

While the preferred embodiments of the invention have been described above, it will be recognized and understood that various modifications can be made in the invention and the appended claims are intended to cover all such modifications which may fall within the spirit and scope of the invention. 

1. A thermoelectric wafer chuck comprising: a wafer support surface for supporting a wafer; and a thermoelectric module provided in thermal contact with said wafer support surface.
 2. The thermoelectric wafer chuck of claim 1 wherein said thermoelectric module comprises a single-layer thermoelectric module.
 3. The thermoelectric wafer chuck of claim 2 wherein said thermoelectric module defines a plurality of heating zones on said wafer support surface.
 4. The thermoelectric wafer chuck of claim 1 wherein said thermoelectric module comprises a stacked thermoelectric module.
 5. The thermoelectric wafer chuck of claim 4 wherein said thermoelectric module defines a plurality of heating zones on said wafer support surface.
 6. The thermoelectric wafer chuck of claim 1 further comprising a chuck base and wherein said wafer support surface is carried by said chuck base.
 7. The thermoelectric wafer chuck of claim 6 further comprising at least one fluid channel extending through said chuck base.
 8. The thermoelectric wafer chuck of claim 7 wherein said at least one fluid channel extends through said chuck base in a single-loop configuration.
 9. The thermoelectric wafer chuck of claim 7 wherein said at least one fluid channel extends through said chuck base in a multi-loop configuration.
 10. A thermoelectric wafer chuck comprising: a chuck base; at least one coil-free fluid channel extending through said chuck base; and a wafer support surface carried by said chuck base.
 11. The thermoelectric wafer chuck of claim 10 wherein said at least one coil-free fluid channel extends through said chuck base in a single-loop configuration.
 12. The coil-free thermoelectric wafer chuck of claim 10 wherein said at least one coil-free fluid channel extends through said chuck base in a multi-loop configuration.
 13. The coil-free thermoelectric wafer chuck of claim 10 further comprising a thermoelectric module provided in said chuck base in thermal contact with said wafer support surface.
 14. The coil-free thermoelectric wafer chuck of claim 13 wherein said thermoelectric module comprises a single-layer thermoelectric module.
 15. The thermoelectric wafer chuck of claim 14 wherein said thermoelectric module defines a plurality of heating zones on said wafer support surface.
 16. The thermoelectric wafer chuck of claim 13 wherein said thermoelectric module comprises a stacked thermoelectric module.
 17. The thermoelectric wafer chuck of claim 16 wherein said thermoelectric module defines a plurality of heating zones on said wafer support surface.
 18. A thermoelectric wafer chuck comprising: a chuck base; a wafer support plate having a wafer support surface for supporting a wafer carried by said chuck base; a chuck interior defined between said chuck base and said wafer support plate; and a thermoelectric module provided in said chuck interior in thermal contact with said wafer support surface.
 19. The thermoelectric wafer chuck of claim 18 further comprising at least one fluid channel provided in said chuck base.
 20. The thermoelectric wafer chuck of claim 19 wherein said at least one coolant channel extends through said chuck base in a single-loop configuration.
 21. The thermoelectric wafer chuck of claim 19 wherein said at least one coolant channel extends through said chuck base in a multi-loop configuration.
 22. The thermoelectric wafer chuck of claim 18 wherein said thermoelectric module comprises a single-layer thermoelectric module.
 23. The thermoelectric wafer chuck of claim 22 wherein said thermoelectric module defines a plurality of heating zones on said wafer support surface.
 24. The thermoelectric wafer chuck of claim 18 wherein said thermoelectric module comprises a stacked thermoelectric module.
 25. The thermoelectric wafer chuck of claim 24 wherein said thermoelectric module defines a plurality of heating zones on said wafer support surface. 